Water-cooling apparatus for engine

ABSTRACT

A water-cooling apparatus for cooling an engine includes a radiator for cooling coolant, a first flow passage connected with the engine, a second flow passage branched from the first flow passage and connected with the radiator, a third flow passage whose one end is connected with the radiator and whose another end is connected with the first flow passage at a downstream from the branched point of the second flow passage, a regulating valve on the first flow passage for regulating a flow volume of the coolant in the radiator, and a pump on the first flow passage for circulating the coolant through the engine and/or the radiator. The regulating valve is configured to flows the coolant from the radiator to the first flow passage when it is opened. The apparatus has a simple circulation flow path, and thereby appropriate cooling can be done by regulating the flow volume.

TECHNICAL FIELD

The present invention relates to a water-cooling apparatus for anengine, especially to a water-cooling apparatus for an engine thatcontrols cooling water by a pump and a regulating valve.

BACKGROUND ART

Well-known is a water-cooling apparatus for an engine that drives anengine-driven pump according to revolving speed of an internalcombustion engine (hereinafter, referred merely as the engine) tocirculate cooling water through a cylinder head and a cylinder block.

Since a flow volume of the cooling water is proportionate to therevolving speed of the engine in such a water-cooling apparatus, theflow volume of the cooling water may become excessively larger when therevolving speed becomes high under a cold condition or at high-speedrunning. Thus, warming-up may delay due to excessive heat radiation ofthe cooling water and a power loss may be subject to be brought. Inaddition, since the flow volume of the cooling water is proportionate tothe revolving speed of the engine, knockings due to the cooling delaymay occur when an engine load increases rapidly due to abruptacceleration or the like.

In order to cool an engine according to an engine load, proposed is awater-cooling apparatus in which a bypass flow passage bypassing aradiator and a special pump for cooling combustion cylinders areprovided (see Patent Document 1).

PRIOR ART DOCUMENT Patent Documents

-   Patent Document 1: Japanese Patent Application Laid-Open No.    2006-161606

SUMMARY OF INVENTION

However, in such a water-cooling apparatus, the number of parts mayincrease and flow passages for cooling water may become complicated.Therefore, an object of the present invention is to provide awater-cooling apparatus for an engine that has a simple circulation flowpath of cooling water and can carry out appropriate cooling byregulating a flow volume of the cooling water flowing through thecirculation flow path.

An aspect of the present invention provides a water-cooling apparatusfor an engine that cools an internal combustion engine by cooling water,the apparatus comprising: a radiator that cools the cooling water byheat-exchanging between the cooling water and air; a first flow passagethat flows the cooling water to the engine; a second flow passage thatis branched from the first flow passage and flows the cooling water tothe radiator; a third flow passage that flows the cooling water flowingfrom the radiator to the first flow passage at a downstream from abranched point of the second flow passage from the first flow passage; aregulating valve that is disposed on the first flow passage andregulates a flow volume of the cooling water flowing through theradiator; and a pump that is disposed on the first flow passage andcirculates the cooling water through the engine and/or the radiator,wherein the regulating valve is configured to flows the cooling waterflowing from the radiator to the first flow passage when opened.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a first embodiment.

FIG. 2 It is a schematic side view showing a layout of the engine.

FIG. 3 (a) is a graph showing relationship between cooling watertemperature and combustion efficiency at a high load condition of theengine, and (b) is a graph showing relationship between cooling watertemperature and combustion efficiency at a low load condition of theengine.

FIG. 4 It is a flowchart of a worm-up control of the water-coolingapparatus.

FIG. 5 It is a schematic diagram showing a flow of the cooling water inthe warm-up control.

FIG. 6 (a) is a schematic perspective view showing natural convection ofthe cooling water in the water-cooled engine, and (b) is a schematicside view thereof.

FIG. 7 It is a flowchart of a normal control of the water-coolingapparatus.

FIG. 8 It is a schematic diagram showing flows of the cooling water inthe normal control (under a low load condition).

FIG. 9 It is a schematic diagram (2) showing flows of the cooling waterin the normal control (under a high load condition).

FIG. 10 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a modified example of the firstembodiment.

FIG. 11 It is a schematic diagram showing a flow of cooling water in awarm-up control in the water-cooling apparatus.

FIG. 12 It is a schematic diagram showing flows of the cooling water ina normal control (under a low load condition) in the water-coolingapparatus.

FIG. 13 It is a schematic diagram showing flows of the cooling water ina normal control (under a high load condition) in the water-coolingapparatus.

FIG. 14 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a second embodiment.

FIG. 15 It is a flowchart of a worm-up control of the water-coolingapparatus.

FIG. 16 It is a schematic diagram showing a flow of cooling water in thewarm-up control.

FIG. 17 It is a flowchart of a normal control of the water-coolingapparatus.

FIG. 18 It is a schematic diagram showing flows of the cooling water inthe normal control (under a low load condition) in the water-coolingapparatus.

FIG. 19 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a modified example of the secondembodiment.

FIG. 20 It is a schematic diagram showing a flow of cooling water in awarm-up control in the water-cooling apparatus.

FIG. 21 It is a schematic diagram showing flows of the cooling water ina normal control (under a low load condition) in the water-coolingapparatus.

FIG. 22 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a third embodiment.

FIG. 23 It is a flowchart of a worm-up control of the water-coolingapparatus.

FIG. 24 It is a schematic diagram showing flows of cooling water in thewarm-up control.

FIG. 25 It is a flowchart of a normal control of the water-coolingapparatus.

FIG. 26 It is a schematic diagram showing flows of the cooling water inthe normal control (under a low load condition).

FIG. 27 It is a schematic configuration diagram of a water-coolingapparatus for an engine according to a modified example of the thirdembodiment.

FIG. 28 It is a schematic diagram showing flows of cooling water in awarm-up control in the water-cooling apparatus.

FIG. 29 It is a schematic diagram showing flows of the cooling water ina normal control (under a low load condition) in the water-coolingapparatus.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments will be explained with reference to thedrawings. In the drawings, identical or equivalent components to eachother are labeled with identical reference numbers, respectively. Notethat the drawings are shown schematically, and dimensions andproportions of the components in the drawings are not shown preciselybut actual dimensions and proportions of the components should beunderstood in consideration of following explanations. In addition,dimensions and proportions of the components may be shown differentlyamong the drawings.

First Embodiment

As shown in FIG. 1, a water-cooling apparatus 1 a according to a firstembodiment cools a water-cooled internal combustion engine (hereinafter,referred merely as the engine) 2 by using cooling water (coolant). Thewater-cooling apparatus 1 a includes a radiator 3, a first flow passage31, a second flow passage 30, a third flow passage 32, a regulatingvalve 11, and a pump 10. In the radiator 3, heats are exchanged betweenthe cooling water of the engine 2 and air, and thereby the cooling wateris cooled. The first flow passage 31 is disposed on a circulation flowpath of the cooling water and on an upstream side from the engine 2 toflow the cooling water into the engine 2. The second flow passage 30 isdisposed on the circulation flow path and on an upstream side from theradiator 3 to flow the cooling water into the radiator 3. The third flowpassage 32 is disposed on the circulation flow path and on a downstreamside from the radiator 3 to flow the cooling water from the radiator 3to the first flow passage 31.

The regulating valve 11 is disposed on the first flow passage 31 toregulate a flow volume of the cooling water flowing through the engine 2and/or the radiator 3. The pump 10 is disposed also on the first flowpassage 31 (on a downstream side from the regulating valve 11) tocirculate the cooling water along the circulation flow path. An upstreamend of the second flow passage 30 is connected with the first flowpassage 31 (the regulating valve 11), and a downstream end thereof isconnected with the radiator 3. An upstream end of the third flow passage32 is connected with the radiator 3, and a downstream end thereof isconnected with the first flow passage 31. When the regulating valve 11is opened, the cooling water flows into the first flow passage 31through the second flow passage 30, radiator 3 and the third flowpassage 32.

As shown in FIG. 2, the engine 2 is inclined with its exhaust side faceddownward. Since the exhaust side of the engine 2 is faced downward, thecooling water flows toward its intake side (upward) due to naturalconvection when the pump 10 is stopped. Therefore, even when the pump 10is stopped, due to natural convection, temperature of the cooling waternear a cylinder head can be homogenized and the cooling water can becirculated thorough the radiator 3. It is preferable that theinclination α(°) of the engine 2 is set to almost 20° in view of naturalconvention of the cooling water. Note that, when an inclination ofcenter axes of combustion cylinders of the engine 2 with respect to thehorizontal direction is denoted as β(°), α=90°−β.

The engine 2 is cooled by the cooling water from the first flow passage31, and then the cooling water flows out to a fourth flow passage 20. Atemperature sensor (not shown) is disposed on the fourth flow passage20. The temperature sensor detects temperature of the cooling waterflowing out from the engine 2 (i.e. in the engine 2). Detected data bythe temperature sensor are output to a controller (not shown).

Combustion efficiency that depends on the temperature of the coolingwater of the engine 2 will be explained with reference to graphs shownin FIG. 3 (a) and (b). When a load applied to the engine 2 (here, theload is indicated by Indicated Mean Effective Pressure: IMEP) is low(low load: 300 kPa), the combustion efficiency (here, the combustionefficiency is indicated by indicated thermal efficiency) is better withhigh temperature of the cooling water, e.g. 100° C. (secondtemperature), as shown in FIG. 3 (a). On the other hand, when a loadapplied to the engine 2 is high (high load: 900 kPa), the combustionefficiency is better with low temperature of the cooling water, e.g. 80°C. (first temperature), as shown in FIG. 3 (b).

The radiator 3 is a device for radiating heats of the engine 2 byintermediary of the cooling water, and has a structure in which manytubes each of which has fins and is made of aluminum alloy or the likeare aligned. A flow-in side of the radiator 3 is connected with thedownstream end of the second flow passage 30, and a flow-out sidethereof is connected with the upstream end of the third flow passage 32.

A heater core 4 is disposed on a downstream side from the fourth flowpassage 20 on the circulation flow path of the cooling water, and itsflow-out side is connected with the pump 10 by a fifth flow passage 22.An electromagnetic valve 25 for regulating a flow volume of the coolingwater is disposed on the fourth flow passage 20 on an upstream side fromthe heater core 4. A flow volume of the cooling water flowing throughthe heater core 4 is regulated by adjusting a valve opening position ofthe electromagnetic valve 25 to adjust a heat radiation amount at theheater core 4. As a result, the temperature of the cooling water is alsoadjusted. The heater core 4 heats air by heat-exchanging between thecooling water heated by the engine 2 and the air. The heated air isutilized for air-conditioning and so on.

Further, a sixth flow passage 24 bypassing the heater core 4 is alsoprovided. An upstream end of the sixth flow passage 24 is connected withthe fourth flow passage 20 on an upstream side from the heater core 4,and a downstream end thereof is connected with the fifth flow passage22. When the electromagnetic valve 25 is closed, the cooling water flowsthorough the sixth flow passage 24 to bypass the heater core 4.

The pump 10 in the present embodiment is an electrical pump P₁ operableindependently from operations of the engine 2. The pump 10 (electricalpump P₁) controls a flow volume of the cooling water based on a signalfrom the controller (not shown).

The regulating valve 11 is disposed on the first flow passage and on adownstream side from the pump 10. The second flow passage 30 is branchedfrom the regulating valve 11. The regulating valve 11 is a three-wayvalve for flowing the cooling water from the pump 10 to the engine 2and/or the second flow passage 30. The regulating valve 11 is anelectrically-controlled thermostat, and controls, with respect to thecooling water from the pump 10, a flow volume of the cooling water flownto the engine 2 and/or the radiator 3 based on a signal from thecontroller (not shown). The regulating valve 11 in the presentembodiment controls a flow volume of the cooling water to be flown tothe radiator 3 at an upstream from the radiator 3.

Hereinafter, a warm-up control of the engine 2 by the water-coolingapparatus 1 a will be explained with reference to a flowchart shown inFIG. 4.

First, it is judged whether or not temperature of the cooling waterdetected by the temperature sensor is equal-to or lower-than the firsttemperature (80° C.) as a reference index for completion of warming-up(step S10). If the temperature of the cooling water is higher than thefirst temperature (80° C.) (NO in step S10), it transitions to a normalcontrol to be carried out after the worm-up control (step S30), and theworm-up control is ended. The normal control will be explained later indetail. On the other hand, if the temperature of the cooling water isequal-to or higher-than the first temperature (80° C.) (YES in stepS10), it is judged whether or not a heater switch of an air-conditioneris turned on (step S11).

If the heater switch is not turned on (NO in step S11), the controllersends control signals for making the temperature of the cooling waterhigher than the first temperature (80° C.) quickly to the pump 10, theregulating valve 11 and the electromagnetic valve 25. Here, since theheater switch is turned off, it is not needed to flow the cooling waterto the heater core 4. Therefore, the electromagnetic valve 25 on theupstream side from the heater core 4 is closed based on the controlsignal from the controller (step S12). Further, the second flow passage30 is also closed by the regulating valve as shown in FIG. 5(after-explained step S14), and thereby the cooling water is not flownto the radiator 3. Thus, heats are not radiated at the radiator 3 andthe heater core 4, and thereby temperature of the cooling water is madehigher than the first temperature (80° C.) quickly.

Subsequent to the step S12, the pump 10 (the electrical pump P₁) isstopped based on the control signal from the controller to stopsupplying the cooling water to the engine 2 (step S13). Since the engine2 is inclined as shown in FIG. 6( a) and (b), the cooling water flowsdue to natural convection even when the pump 10 is stopped. Therefore,without forcibly circulating the cooling water by the pump 10, thecooling water circulates in the water-cooling apparatus 1 a due tonatural convection. But, according to this, temperature of the coolingwater in the engine 2 is raised quickly to suitable temperature for heatefficiency due to absorption of heats of the engine 2.

Subsequent to the step S13, the regulating valve 11 closes the secondflow passage 30 (at its upstream end) based on the control signal fromthe controller (step S14). Heats are not radiated at the radiator 3 dueto the closure of the second flow passage 30, and thereby thetemperature of the cooling water can be prevented from reducing duringthe warm-up control. After the step S14, the process flow is returned tothe step S10, and then it transitions to the normal control (step S30)when the temperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11(YES in step S11), the electromagnetic valve 25 on the upstream sidefrom the heater core 4 is controlled to flow the cooling water to theheater core 4 for air-heating. Specifically, a valve opening position ofthe electromagnetic valve 25 is set so as to flow the cooling water tothe heater core 4 by 10 L/min based on the control signal from thecontroller (step S20).

Subsequent to the step S20, also a discharge volume of the pump 10 isalso controlled so as to flow the cooling water to the heater core 4 by10 L/min based on the control signal from the controller (step S21).Here, since natural convection also occurs due to the inclination of theengine 2 shown in FIG. 6( a) and (b), energy required for driving thepump 10 can be reduced. Namely, the flow volume 10 L/min of the coolingwater is achieved by the valve opening position of the electromagneticvalve 25 and the discharge volume of the pump 10.

Subsequent to the step S21, the regulating valve 11 closes the secondflow passage 30 based on the control signal from the controller (stepS22). Heats are not radiated at the radiator 3 due to the closure of thesecond flow passage 30, and thereby the temperature of the cooling watercan be prevented from reducing during the warm-up control. Althoughheats are radiated at the heater core 4 for air-heating, heats are notradiated at the radiator 3 and thereby the temperature of the coolingwater will become higher than the first temperature (80° C.) quickly.After the step S22, the process flow is returned to the step S10, andthen it transitions to the normal control (step S30) when thetemperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) bythe water-cooling apparatus 1 a will be explained with reference to aflowchart shown in FIG. 7.

First, it is judged whether or not the engine 2 is idled (step S110). Ifit is not idled (NO in step S110), it is judged whether or not a changeof a throttle position is small in order to estimate an operation stateof the engine 2 (step S111). The throttle position is a valve openingposition of a throttle valve that is disposed on an intake air passageof the engine 2 to regulate an intake air volume (note that, in a caseof an engine having an intake air volume control mechanism without athrottle valve, the change of a throttle position may mean a change ofan intake air volume parameter). A case where the change of a throttleposition is small is a steady state such as constant-speed running orthe like, i.e. a case where the engine 2 is operated with a low load. Onthe other hand, a case where the change of a throttle position is largeis a transient state such as accelerating running, hill-climbing runningor the like, i.e. a case where the engine 2 is operated with a highload.

If the change of a throttle position is small (smaller than apredetermined change of an opening position), i.e. the engine 2 is in alow-load state (YES in step S111), the controller sends control signalsfor regulating the temperature of the cooling water to be the secondtemperature (100° C.) to the pump 10, the regulating valve 11 and theelectromagnetic valve 25. Since, in a low-load state of the engine 2,fuel efficiency is better when the temperature of the cooling water isthe second temperature (100° C.) higher than the first temperature (80°C.) as shown in FIG. 3( a), the temperature of the cooling water isregulated to be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagneticvalve 25 is opened based on the control signal from the controller tocirculate the cooling water through the heater core 4 (step S112).According to this, an air-conditioner can use heats of the heater core 4at any time. Note that, since it is in a low-load state with no changeof a throttle position when idled in the step S110 (YES in step S110),the process flow proceeds to the step S112 without the judgment of thestep S111.

Subsequent to the step S112, the pump 10 (the electrical pump P₁)circulates the cooling water based on the control signal from thecontroller, but its flow volume is controlled to be small (step S113).Heat radiation at the heater core 4 and the radiator 3 is restricted bymaking the flow volume small, and thereby the temperature of the coolingwater rises and becomes the second temperature (100° C.) (a flow of thecooling water to the radiator 3 will be explained in a next step S114).

Subsequent to the step S113, a valve opening position of the regulatingvalve 11 is adjusted based on the control signal from the controller toadjust a flow volume of the cooling water flowing through the radiator 3at the upstream end of the second flow passage 30 (step S114). In orderto regulate the temperature of the cooling water to be the secondtemperature (100° C.) by restricting heat radiation at the radiator 3, aflow volume to the second flow passage 30, the radiator 3 and the thirdflow passage 32 is made relatively small (see FIG. 8). Note that theregulating valve 11 also flows the cooling water from the pump 10 to theengine 2.

On the other hand, if the change of a throttle position is large (largerthan the predetermined change of an opening position), i.e. the engine 2is in a high-load state (NO in step S111), the controller sends controlsignals for regulating the temperature of the cooling water to be thefirst temperature (80° C.) to the pump 10, the regulating valve 11 andthe electromagnetic valve 25. Since, in a high-load state of the engine2, fuel efficiency is better when the temperature of the cooling wateris the first temperature (80° C.) lower than the second temperature(100° C.) as shown in FIG. 3( b), the temperature of the cooling wateris regulated to be the first temperature (80° C.).

Specifically, similarly to the above-explained step S112, since theworming-up is completed, the electromagnetic valve 25 is opened based onthe control signal from the controller to circulate the cooling waterthrough the heater core 4 (step S120). Subsequent to the step S120, thepump 10 (the electrical pump P₁) circulates the cooling water based onthe control signal from the controller, but its flow volume iscontrolled to be large (step S121). Heat radiation at the radiator 3 ispromoted by making the flow volume large, and thereby the temperature ofthe cooling water is restricted from rising and kept at the firsttemperature (80° C.) (a flow of the cooling water to the radiator 3 willbe explained in a next step S122).

Subsequent to the step S121, a valve opening position of the regulatingvalve 11 is adjusted based on the control signal from the controller toclose a flow path to the first flow passage 31 connected with the engine2 and to fully-open a valve opening position of the upstream end of thesecond flow passage 30 (step S122), and thereby the cooling water isflown only to the second flow passage 30, the radiator 3 and the thirdflow passage 32 (see FIG. 9). In order to regulate the temperature ofthe cooling water to be the first temperature (80° C.) by promoting heatradiation at the radiator 3, a flow volume to the second flow passage30, the radiator 3 and the third flow passage 32 is made large. Thecooling water flows through the second flow passage 30, the radiator 3and the third flow passage 32, and then flows into the engine 2. Thus,the heat radiation at the radiator 3 is promoted, and thereby thetemperature of the cooling water is reduced to become the firsttemperature (80° C.).

According to the water-cooling apparatus 1 a in the present embodiment,since the third flow passage 32 for flowing the cooling water out fromthe radiator 3 to the engine 2, the temperature control and the flowvolume control of the cooling water can be easily done withoutincreasing the number of parts and without complicating the flowpassages of the cooling water.

Further, the third flow passage 32 in a low-load state (see FIG. 8) isfilled with the cooling water at about 60° C. that is cooled at theradiator 3. Here, when the cooling water is crammed into the radiator 3thorough the second flow passage 30 by the regulating valve 11, thecooling water in the third flow passage 32 flows into the engine 2 afterbecoming confluent with the cooling water in the first flow passage 31because water is incompressible fluid. Therefore, when a flow volume tothe second flow passage 30 is increased by the regulating valve 11 attransition from a low-load state to a high-load state such as abruptacceleration (FIG. 8 to FIG. 9), the cooling water at about 60° C. inthe third flow passage 32 is made confluent with the cooling water inthe first flow passage 31 and then the cooling water flows into theengine 2. As a result, it becomes possible to change the temperature ofthe cooling water instantaneously from the second temperature (100° C.)for a low-load state to the first temperature (80° C.) for a high-loadstate. In a low-load state, fuel consumption can be improved by about 3%by regulating the cooling water to be the second temperature (100° C.)that brings good combustion efficiency. Furthermore, it becomes possibleto prevent knockings in a high-load state (accelerating running) byquickly reducing the temperature of the cooling water to the firsttemperature (80° C.).

Modified Example of First Embodiment

As shown in FIG. 10, a position of a regulating valve 11 in awater-cooling apparatus 1 a′ for an engine according to a modifiedexample of the first embodiment is different from that in thewater-cooling apparatus 1 a according to the first embodiment (see FIG.1). Since other configurations of the water-cooling apparatus 1 a′ inthe present modified example are identical to those of the water-coolingapparatus 1 a according to the first embodiment, their redundantexplanations will be omitted.

The regulating valve 11 in the present modified example is also athree-way disposed on the first flow passage and on a downstream sidefrom the pump 10. But, whereas the regulating valve 11 in the firstembodiment is disposed at a branch point of the second flow passage 30on the first flow passage 31, the regulating valve 11 in the presentmodified example is disposed at a confluent point of the third flowpassage 32 on the first flow passage 31. The regulating valve 11 is anelectrically-controlled thermostat, and controls a flow volume of thecooling water to be flown to the to the engine 2 and/or the radiator 3based on the signals from the controller (not shown) by controlling amixture rate of the cooling water from the pump 10 and the cooling waterfrom the third flow passage 32. The regulating valve 11 in the presentmodified example controls a flow volume of the cooling water to be flownto the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1 a′ isdifferent from the warm-up control in the first embodiment in theprocesses of the steps S14 and S22 (see FIG. 4) that relate to theregulating valve 11. Since a whole of the warm-up control is carried outin line with the flowchart shown in FIG. 4 also in the present modifiedexample, only the different steps S14 and S22 will be explainedhereinafter.

In the step S14, the temperature of the cooling water is equal-to orlower-than the first temperature (80° C.) (YES in step S10) and theheater switch is turned off (NO in step S11). Therefore, heats are notradiated at the radiator 3 and the heater core 4, and thereby thecooling water is made higher than the first temperature (80° C.)quickly. Namely, as shown in FIG. 11, the electromagnetic valve 25 isclosed (step S12) and the pump 10 is stopped (step S13). Further, theregulating valve 11 closes the third flow passage 32 (at its downstreamend) based on the control signal from the controller (step S14).

On the other hand, in the step S22, the temperature of the cooling wateris equal-to or lower-than the first temperature (80° C.) (YES in stepS10) and the heater switch is turned on (YES in step S11). Therefore,heats are not radiated at the radiator 3, and thereby the cooling wateris made higher than the first temperature (80° C.) quickly. Namely, theelectromagnetic valve 25 is opened (step S20: to radiates heats at theheater core 4 because the heater switch is turned on) and the pump 10 isdriven (step S21). Further, the regulating valve 11 closes the thirdflow passage 32 (at its downstream end) based on the control signal fromthe controller (step S22).

A normal control (after the warm-up control) by the water-coolingapparatus 1 a′ is different from the normal control in the firstembodiment in the processes of the steps S114 and S122 (see FIG. 7) thatrelate to the regulating valve 11. Since a whole of the normal controlis carried out in line with the flowchart shown in FIG. 7 also in thepresent modified example, only the different steps S114 and S122 will beexplained hereinafter.

In the step S114, since the engine 2 is idled (YES in step S110) or thechange of a throttle position is small (YES in step S111), the engine 2is in a low-load state. Therefore, the pump 10 is controlled so that aflow volume of the cooling water becomes small (step S113) to restrictheat radiation at the heater core 4 and the radiator 3, and thereby thetemperature of the cooling water is raised to the second temperature(100°). In addition, a valve opening position of the regulating valve 11is adjusted based on the control signal from the controller, and therebya flow volume of the cooling water flowing through the radiator 3 isadjusted at the downstream end of the third flow passage 32 (step S114).In order to regulate the temperature of the cooling water to be thesecond temperature (100° C.) by restricting heat radiation at theradiator 3, a flow volume to the second flow passage 30, the radiator 3and the third flow passage 32 is made relatively small (see FIG. 12).Note that the regulating valve 11 also flows the cooling water from thepump 10 to the engine 2.

On the other hand, in the step S122, since the change of a throttleposition is large (NO in step S111), the engine 2 is in a high-loadstate. Therefore, the pump 10 is controlled so that a flow volume of thecooling water becomes large (step S121) to promote heat radiation at theheater core 4 and the radiator 3, and thereby the temperature of thecooling water is regulated to be the first temperature (80°). Namely, avalve opening position of the regulating valve 11 is adjusted based onthe control signal from the controller to close a flow path from thefirst flow passage 31 and to fully-open a valve opening position of thedownstream end of the third flow passage 32 (step S122), and thereby thecooling water is flown only to the second flow passage 30, the radiator3 and the third flow passage 32 (see FIG. 13).

Advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-coolingapparatus 1 a′ in the present modified example that is configures asexplained above.

Second Embodiment

As shown in FIG. 14, a water-cooling apparatus 1 b for an engineaccording to a second embodiment has a configuration in which the pump10 (the electrical water pump P₁) of the water-cooling apparatus 1 a inthe first embodiment (see FIG. 1) is replaced with a pump 12 (anengine-driven pump P₂) driven by the engine 2. Therefore, according tothe pump 12 in the present embodiment, a flow volume of the coolingwater varies along with an engine revolving speed. Since otherconfigurations of the water-cooling apparatus 1 b in the presentembodiment are identical to those of the water-cooling apparatus 1 a inthe first embodiment, their redundant explanations will be omitted.

Hereinafter, a warm-up control of the engine 2 by the water-coolingapparatus 1 b will be explained with reference to a flowchart shown inFIG. 15.

First, it is judged whether or not temperature of the cooling waterdetected by the temperature sensor is equal-to or lower-than the firsttemperature (80° C.) as a reference index for completion of warming-up(step S10). If the temperature of the cooling water is higher than thefirst temperature (80° C.) (NO in step S10), it transitions to a normalcontrol to be carried out after the worm-up control (step S30), and theworm-up control is ended. The normal control will be explained later indetail. On the other hand, if the temperature of the cooling water isequal-to or lower-than the first temperature (80° C.) (YES in step S10),it is judged whether or not a heater switch of an air-conditioner isturned on (step S11).

If the heater switch is not turned on (NO in step S11), the controllersends control signals for making the temperature of the cooling waterhigher than the first temperature (80° C.) quickly to the regulatingvalve 11 and the electromagnetic valve 25. Here, since the heater switchis turned off, it is not needed to flow the cooling water to the heatercore 4. Therefore, the electromagnetic valve 25 on the upstream sidefrom the heater core 4 is closed based on the control signal from thecontroller (step S12). Further, the second flow passage 30 is alsoclosed by the regulating valve 11 as shown in FIG. 16 (after-explainedstep S14), and thereby the cooling water is not flown to the radiator 3.Thus, heats are not radiated at the radiator 3 and the heater core 4,and thereby temperature of the cooling water is made higher than thefirst temperature (80° C.) quickly.

Subsequent to the step S12, the regulating valve 11 closes the secondflow passage 30 (at its upstream end) based on the control signal fromthe controller (step S14). Heats are not radiated at the radiator 3 dueto the closure of the second flow passage 30, and thereby thetemperature of the cooling water can be prevented from reducing duringthe warm-up control. After the step S14, the process flow is returned tothe step S10, and then it transitions to the normal control (step S30)when the temperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11(YES in step S11), the electromagnetic valve 25 on the upstream sidefrom the heater core 4 is controlled to flow the cooling water to theheater core 4 for air-heating. Specifically, a valve opening position ofthe electromagnetic valve 25 is set so as to flow the cooling water tothe heater core 4 by 10 L/min based on the control signal from thecontroller (step S20).

Subsequent to the step S20, the regulating valve 11 closes the secondflow passage 30 based on the control signal from the controller (stepS22). Heats are not radiated at the radiator 3 due to the closure of thesecond flow passage 30, and thereby the temperature of the cooling watercan be prevented from reducing during the warm-up control. Althoughheats are radiated at the heater core 4 for air-heating, heats are notradiated at the radiator 3 and thereby the temperature of the coolingwater will become higher than the first temperature (80° C.) quickly.After the step S22, the process flow is returned to the step S10, andthen it transitions to the normal control (step S30) when thetemperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) bythe water-cooling apparatus 1 b will be explained with reference to aflowchart shown in FIG. 17.

First, it is judged whether or not the engine 2 is idled (step S110). Ifit is not idled (NO in step S110), it is judged whether or not a changeof a throttle position is small in order to estimate an operation stateof the engine 2 (step S111).

If the change of a throttle position is small, i.e. the engine 2 is in alow-load state (YES in step S111), the controller sends control signalsfor regulating the temperature of the cooling water to be the secondtemperature (100° C.) to the regulating valve 11 and the electromagneticvalve 25. Since, in a low-load state of the engine 2, fuel efficiency isbetter when the temperature of the cooling water is the secondtemperature (100° C.) higher than the first temperature (80° C.) asshown in FIG. 3 (a), the temperature of the cooling water is regulatedto be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagneticvalve 25 is opened based on the control signal from the controller tocirculate the cooling water through the heater core 4 (step S112).According to this, an air-conditioner can use heats of the heater core 4at any time. Note that, since it is in a low-load state with no changeof a throttle position when idled in the step S110 (YES in step S110),the process flow proceeds to the step S112 without the judgment of thestep S111.

Subsequent to the step S112, a valve opening position of the regulatingvalve 11 is adjusted based on the control signal from the controller toadjust a flow volume of the cooling water flowing through the radiator 3at the upstream end of the second flow passage 30 (step S114). In orderto regulate the temperature of the cooling water to be the secondtemperature (100° C.) by restricting heat radiation at the radiator 3, aflow volume to the second flow passage 30, the radiator 3 and the thirdflow passage 32 is made relatively small (see FIG. 18). Note that theregulating valve 11 also flows the cooling water from the pump 12 to theengine 2.

On the other hand, if the change of a throttle position is large, i.e.the engine 2 is in a high-load state (NO in step S111), the controllersends control signals for regulating the temperature of the coolingwater to be the first temperature (80° C.) to the regulating valve 11and the electromagnetic valve 25. Since, in a high-load state of theengine 2, fuel efficiency is better when the temperature of the coolingwater is the first temperature (80° C.) lower than the secondtemperature (100° C.) as shown in FIG. 3( b), the temperature of thecooling water is regulated to be the first temperature (80° C.).

Specifically, similarly to the above-explained step S112, since theworming-up is completed, the electromagnetic valve 25 is opened based onthe control signal from the controller to circulate the cooling waterthrough the heater core 4 (step S120). Subsequent to the step S120, avalve opening position of the regulating valve 11 is adjusted based onthe control signal from the controller to close a flow path to the firstflow passage 31 connected with the engine 2 and to fully-open a valveopening position of the upstream end of the second flow passage 30 (stepS122), and thereby the cooling water is flown only to the second flowpassage 30, the radiator 3 and the third flow passage 32 (similar toFIG. 9: however, not the pump 10 but the pump 12). In order to regulatethe temperature of the cooling water to be the second temperature (100°C.) by restricting heat radiation at the radiator 3, a flow volume tothe second flow passage 30, the radiator 3 and the third flow passage 32is made large. The cooling water flows through the second flow passage30, the radiator 3 and the third flow passage 32, and then flows intothe engine 2. Thus, the heat radiation at the radiator 3 is promoted,and thereby the temperature of the cooling water is reduced to becomethe first temperature (80° C.).

Advantages equivalent to those brought by the water-cooling apparatus 1a in the first embodiment can be also brought by the water-coolingapparatus 1 b in the present embodiment that is configures as explainedabove.

Modified Example of Second Embodiment

As shown in FIG. 19, a position of a regulating valve 11 in awater-cooling apparatus 1 b′ for an engine according to a modifiedexample of the second embodiment is different from that in thewater-cooling apparatus 1 b according to the second embodiment (see FIG.14). Since other configurations of the water-cooling apparatus 1 b′ inthe present modified example are identical to those of the water-coolingapparatus 1 b according to the second embodiment, their redundantexplanations will be omitted.

The regulating valve 11 in the present modified example is also athree-way disposed on the first flow passage and on a downstream sidefrom the pump 12. But, whereas the regulating valve 11 in the secondembodiment is disposed at a branch point of the second flow passage 30on the first flow passage 31, the regulating valve 11 in the presentmodified example is disposed at a confluent point of the third flowpassage 32 on the first flow passage 31. The regulating valve 11 is anelectrically-controlled thermostat, and controls a flow volume of thecooling water to be flown to the to the engine 2 and/or the radiator 3based on the signals from the controller (not shown) by controlling amixture rate of the cooling water from the pump 12 and the cooling waterfrom the third flow passage 32. The regulating valve 11 in the presentmodified example controls a flow volume of the cooling water to be flownto the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1 b′ isdifferent from the warm-up control in the second embodiment in theprocesses of the steps S14 and S22 (see FIG. 15) that relate to theregulating valve 11. Since a whole of the warm-up control is carried outin line with the flowchart shown in FIG. 15 also in the present modifiedexample, only the different steps S14 and S22 will be explainedhereinafter.

In the step S14, the temperature of the cooling water is equal-to orlower-than the first temperature (80° C.) (YES in step S10) and theheater switch is turned off (NO in step S11). Therefore, heats are notradiated at the radiator 3 and the heater core 4, and thereby thecooling water is made higher than the first temperature (80° C.)quickly. Namely, as shown in FIG. 20, the electromagnetic valve 25 isclosed (step S12) and the regulating valve 11 closes the third flowpassage 32 (at its downstream end) based on the control signal from thecontroller (step S14).

On the other hand, in the step S22, the temperature of the cooling wateris equal-to or lower-than the first temperature (80° C.) (YES in stepS10) and the heater switch is turned on (YES in step S11). Therefore,heats are not radiated at the radiator 3, and thereby the cooling wateris made higher than the first temperature (80° C.) quickly. Namely, theelectromagnetic valve 25 is opened (step S20: to radiates heats at theheater core 4 because the heater switch is turned on) and the regulatingvalve 11 closes the third flow passage 32 (at its downstream end) basedon the control signal from the controller (step S22).

A normal control (after the warm-up control) by the water-coolingapparatus 1 b′ is different from the normal control in the secondembodiment in the processes of the steps S114 and S122 (see FIG. 17)that relate to the regulating valve 11. Since a whole of the normalcontrol is carried out in line with the flowchart shown in FIG. 17 alsoin the present modified example, only the different steps S114 and S122will be explained hereinafter.

In the step S114, since the engine 2 is idled (YES in step S110) or thechange of a throttle position is small (YES in step S111), the engine 2is in a low-load state. Therefore, the regulating valve 11 is controlledso that a flow volume of the cooling water to the radiator 3 becomessmall to restrict heat radiation at the radiator 3, and thereby thetemperature of the cooling water is raised to the second temperature(100°). Namely, a valve opening position of the regulating valve 11 isadjusted based on the control signal from the controller, and thereby aflow volume of the cooling water flowing through the radiator 3 isadjusted at the downstream end of the third flow passage 32 (step S114).In order to regulate the temperature of the cooling water to be thesecond temperature (100° C.) by restricting heat radiation at theradiator 3, a flow volume to the second flow passage 30, the radiator 3and the third flow passage 32 is made relatively small (see FIG. 21).Note that the regulating valve 11 also flows the cooling water from thepump 12 to the engine 2.

On the other hand, in the step S122, since the change of a throttleposition is large (NO in step S111), the engine 2 is in a high-loadstate. Therefore, the regulating valve 11 is controlled so that a flowvolume of the cooling water becomes large to promote heat radiation atthe radiator 3, and thereby the temperature of the cooling water isregulated to be the first temperature (80°). Namely, a valve openingposition of the regulating valve 11 is adjusted based on the controlsignal from the controller to close a flow path from the first flowpassage 31 and to fully-open a valve opening position of the downstreamend of the third flow passage 32 (step S122), and thereby the coolingwater is flown only to the second flow passage 30, the radiator 3 andthe third flow passage 32 (similar to FIG. 13: however, not the pump 10but the pump 12).

Advantages equivalent to those brought by the water-cooling apparatus 1b in the second embodiment, i.e. advantages equivalent to those broughtby the water-cooling apparatus 1 a in the first embodiment can be alsobrought by the water-cooling apparatus 1 b′ in the present modifiedexample that is configures as explained above.

Third Embodiment

As shown in FIG. 22, a water-cooling apparatus 1 c for an engineaccording to a third embodiment has a configuration in which an on-offvalve 13 is added to the water-cooling apparatus 1 b in the secondembodiment (see FIG. 14). One side (flow-out side) of the on-off valve13 is connected with the fifth flow passage 22 (an upstream side fromthe pump 12), and another side (flow-in) thereof is connected with thefirst flow passage 31 (a downstream side from the pump 12, and anupstream side from the regulating valve 11). The on-off valve 13regulates a flow volume of the cooling water to the regulating valve 11(i.e. the engine 2). Since other configurations of the water-coolingapparatus ic in the present embodiment are identical to those of thewater-cooling apparatus 1 b in the second embodiment, their redundantexplanations will be omitted.

Hereinafter, a warm-up control of the engine 2 by the water-coolingapparatus 1 c will be explained with reference to a flowchart shown inFIG. 23.

First, it is judged whether or not temperature of the cooling waterdetected by the temperature sensor is equal-to or lower-than the firsttemperature (80° C.) as a reference index for completion of warming-up(step S10). If the temperature of the cooling water is higher than thefirst temperature (80° C.) (NO in step S10), it transitions to a normalcontrol to be carried out after the worm-up control (step S30), and theworm-up control is ended. The normal control will be explained later indetail. On the other hand, if the temperature of the cooling water isequal-to or lower-than the first temperature (80° C.) (YES in step S10),it is judged whether or not a heater switch of an air-conditioner isturned on (step S11).

If the heater switch is not turned on (NO in step S11), the controllersends control signals for making the temperature of the cooling waterhigher than the first temperature (80° C.) quickly to the regulatingvalve 11, the electromagnetic valve 25 and the on-off valve 13. Here,since the heater switch is turned off, it is not needed to flow thecooling water to the heater core 4. Therefore, the electromagnetic valve25 on the upstream side from the heater core 4 is closed based on thecontrol signal from the controller (step S12). Further, the second flowpassage 30 is also closed by the regulating valve 11 as shown in FIG. 24(after-explained step S14), and thereby the cooling water is not flownto the radiator 3. Thus, heats are not radiated at the radiator 3 andthe heater core 4, and thereby temperature of the cooling water is madehigher than the first temperature (80° C.) quickly.

Subsequent to the step S12, the on-off valve 13 is opened based on thecontrol signal from the controller (step S15). When the on-off valve 13is opened, the cooling water is recirculated from a downstream side(high-pressure side) of the pump 12 to an upstream side (low-pressureside) thereof as shown in FIG. 24, and thereby a flow volume to theregulating valve 11 (i.e. the engine 2) is reduced. By reducing the flowvolume to the engine 2, temperature of the cooling water in the engine 2is raised quickly to suitable temperature for heat efficiency due toabsorption of heats of the engine 2.

Subsequent to the step S15, the regulating valve 11 closes the secondflow passage 30 (at its upstream end) based on the control signal fromthe controller (step S16). Heats are not radiated at the radiator 3 dueto the closure of the second flow passage 30, and thereby thetemperature of the cooling water can be prevented from reducing duringthe warm-up control. After the step S16, the process flow is returned tothe step S10, and then it transitions to the normal control (step S30)when the temperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

On the other hand, if the heater switch is turned on in the step S11(YES in step S11), the electromagnetic valve 25 on the upstream sidefrom the heater core 4 is controlled to flow the cooling water to theheater core 4 for air-heating. Specifically, a valve opening position ofthe electromagnetic valve 25 is set so as to flow the cooling water tothe heater core 4 by 10 L/min based on the control signal from thecontroller (step S20).

Subsequent to the step S20, the on-off valve 13 is closed based on thecontrol signal from the controller (step S23). When the on-off valve 13is closed, the cooling water is not recirculated and a flow volume tothe regulating valve 11 (i.e. the engine 2) is not reduced.

Subsequent to the step S23, the regulating valve 11 closes the secondflow passage 30 based on the control signal from the controller (stepS24). Heats are not radiated at the radiator 3 due to the closure of thesecond flow passage 30, and thereby the temperature of the cooling watercan be prevented from reducing during the warm-up control. Althoughheats are radiated at the heater core 4 for air-heating, heats are notradiated at the radiator 3 and thereby the temperature of the coolingwater will become higher than the first temperature (80° C.) quickly.After the step S24, the process flow is returned to the step S10, andthen it transitions to the normal control (step S30) when thetemperature of the cooling water becomes higher than the firsttemperature (80° C.) (NO in step S10).

Next, a normal control of the engine 2 (after the warm-up control) bythe water-cooling apparatus 1 c will be explained with reference to aflowchart shown in FIG. 25.

First, it is judged whether or not the engine 2 is idled (step S110). Ifit is not idled (NO in step S110), it is judged whether or not a changeof a throttle position is small in order to estimate an operation stateof the engine 2 (step S111).

If the change of a throttle position is small, i.e. the engine 2 is in alow-load state (YES in step S111), the controller sends control signalsfor regulating the temperature of the cooling water to be the secondtemperature (100° C.) to the regulating valve 11, the electromagneticvalve 25 and the on-off valve 13. Since, in a low-load state of theengine 2, fuel efficiency is better when the temperature of the coolingwater is the second temperature (100° C.) higher than the firsttemperature (80° C.) as shown in FIG. 3( a), the temperature of thecooling water is regulated to be the second temperature (100° C.).

Specifically, since the worming-up is completed, the electromagneticvalve 25 is opened based on the control signal from the controller tocirculate the cooling water through the heater core 4 (step S112).According to this, an air-conditioner can use heats of the heater core 4at any time. Note that, since it is in a low-load state with no changeof a throttle position when idled in the step S110 (YES in step S110),the process flow proceeds to the step S112 without the judgment of thestep S111.

Subsequent to the step S112, the on-off valve 13 is closed based on thecontrol signal from the controller (step S115). When the on-off valve 13is closed, the cooling water is not recirculated and a flow volume tothe regulating valve 11 (i.e. the engine 2) is not reduced.

Subsequent to the step S115, a valve opening position of the regulatingvalve 11 is adjusted based on the control signal from the controller toadjust a flow volume of the cooling water flowing through the radiator 3at the upstream end of the second flow passage 30 (step S116). In orderto regulate the temperature of the cooling water to be the secondtemperature (100° C.) by restricting heat radiation at the radiator 3, aflow volume to the second flow passage 30, the radiator 3 and the thirdflow passage 32 is made relatively small (see FIG. 26). Note that theregulating valve 11 also flows the cooling water from the pump 12 to theengine 2.

On the other hand, if the change of a throttle position is large, i.e.the engine 2 is in a high-load state (NO in step S111), the controllersends control signals for regulating the temperature of the coolingwater to be the first temperature (80° C.) to the regulating valve 11,the electromagnetic valve 25 and the on-off valve 13. Since, in ahigh-load state of the engine 2, fuel efficiency is better when thetemperature of the cooling water is the first temperature (80° C.) lowerthan the second temperature (100° C.) as shown in FIG. 3( b), thetemperature of the cooling water is regulated to be the firsttemperature (80° C.).

Specifically, similarly to the above-explained step S112, since theworming-up is completed, the electromagnetic valve 25 is opened based onthe control signal from the controller to circulate the cooling waterthrough the heater core 4 (step S120). Subsequent to the step S120, theon-off valve 13 is closed based on the control signal from thecontroller (step S123). When the on-off valve 13 is closed, the coolingwater is not recirculated and a flow volume to the regulating valve 11(i.e. the engine 2) is not reduced. Since a flow volume to theregulating valve 11 (i.e. the engine 2) is not reduced, a flow volume ofthe cooling water circulating in the cooling apparatus 1 c is controlledto be large. Heat radiation at the radiator 3 is promoted by making theflow volume large, and thereby the temperature of the cooling water isrestricted from rising and kept at the first temperature (80° C.) (aflow of the cooling water to the radiator 3 will be explained in a nextstep S124).

Subsequent to the step S123, a valve opening position of the regulatingvalve 11 is adjusted based on the control signal from the controller toclose a flow path to the first flow passage 31 connected with the engine2 and to fully-open a valve opening position of the upstream end of thesecond flow passage 30 (step S124), and thereby the cooling water isflown only to the second flow passage 30, the radiator 3 and the thirdflow passage 32. In order to regulate the temperature of the coolingwater to be the first temperature (80° C.) by promoting heat radiationat the radiator 3, a flow volume to the second flow passage 30, theradiator 3 and the third flow passage 32 is made large. The coolingwater flows through the second flow passage 30, the radiator 3 and thethird flow passage 32, and then flows into the engine 2. Thus, the heatradiation at the radiator 3 is promoted, and thereby the temperature ofthe cooling water is reduced to become the first temperature (80° C.).

Advantages equivalent to those brought by the water-cooling apparatus 1b in the second embodiment, i.e. advantages equivalent to those broughtby the water-cooling apparatus 1 a in the first embodiment can be alsobrought by the water-cooling apparatus Ic in the present embodiment thatis configures as explained above.

Modified Example of Third Embodiment

As shown in FIG. 27, a position of a regulating valve 11 in awater-cooling apparatus 1 c′ for an engine according to a modifiedexample of the third embodiment is different from that in thewater-cooling apparatus 1 c according to the third embodiment (see FIG.22). Since other configurations of the water-cooling apparatus 1 c′ inthe present modified example are identical to those of the water-coolingapparatus 1 c according to the third embodiment, their redundantexplanations will be omitted.

The regulating valve 11 in the present modified example is also athree-way disposed on the first flow passage and on a downstream sidefrom the pump 12. But, whereas the regulating valve 11 in the thirdembodiment is disposed at a branch point of the second flow passage 30on the first flow passage 31, the regulating valve 11 in the presentmodified example is disposed at a confluent point of the third flowpassage 32 on the first flow passage 31. The regulating valve 11 is anelectrically-controlled thermostat, and controls a flow volume of thecooling water to be flown to the to the engine 2 and/or the radiator 3based on the signals from the controller (not shown) by controlling amixture rate of the cooling water from the pump 12 and the cooling waterfrom the third flow passage 32. The regulating valve 11 in the presentmodified example controls a flow volume of the cooling water to be flownto the radiator 3 at a downstream from the radiator 3.

A warm-up control of the engine 2 by the water-cooling apparatus 1 c′ isdifferent from the warm-up control in the third embodiment in theprocesses of the steps S16 and S24 (see FIG. 23) that relate to theregulating valve 11. Since a whole of the warm-up control is carried outin line with the flowchart shown in FIG. 23 also in the present modifiedexample, only the different steps S16 and S24 will be explainedhereinafter.

In the step S16, the temperature of the cooling water is equal-to orlower-than the first temperature (80° C.) (YES in step S10) and theheater switch is turned off (NO in step S11). Therefore, heats are notradiated at the radiator 3 and the heater core 4, and thereby thecooling water is made higher than the first temperature (80° C.)quickly. Namely, as shown in FIG. 28, the electromagnetic valve 25 isclosed (step S12) and the on-off valve 13 is opened (step S15). Further,the regulating valve 11 closes the third flow passage 32 (at itsdownstream end) based on the control signal from the controller (stepS16).

On the other hand, in the step S26, the temperature of the cooling wateris equal-to or lower-than the first temperature (80° C.) (YES in stepS10) and the heater switch is turned on (YES in step S11). Therefore,heats are not radiated at the radiator 3, and thereby the cooling wateris made higher than the first temperature (80° C.) quickly. Namely, theelectromagnetic valve 25 is opened (step S20: to radiates heats at theheater core 4 because the heater switch is turned on) and the on-offvalve 13 is closed (step S23). Further, the regulating valve 11 closesthe third flow passage 32 (at its downstream end) based on the controlsignal from the controller (step S26).

A normal control (after the warm-up control) by the water-coolingapparatus 1 c′ is different from the normal control in the thirdembodiment in the processes of the steps S116 and S124 (see FIG. 25)that relate to the regulating valve 11. Since a whole of the normalcontrol is carried out in line with the flowchart shown in FIG. 25 alsoin the present modified example, only the different steps S116 and S124will be explained hereinafter.

In the step S116, since the engine 2 is idled (YES in step S110) or thechange of a throttle position is small (YES in step S111), the engine 2is in a low-load state. Therefore, the regulating valve 11 is controlledso that a flow volume of the cooling water to the radiator 3 becomessmall to restrict heat radiation at the radiator 3, and thereby thetemperature of the cooling water is raised to the second temperature(100°). Namely, a valve opening position of the regulating valve 11 isadjusted based on the control signal from the controller, and thereby aflow volume of the cooling water flowing through the radiator 3 isadjusted at the downstream end of the third flow passage 32 (step S116).In order to regulate the temperature of the cooling water to be thesecond temperature (100° C.) by restricting heat radiation at theradiator 3, a flow volume to the second flow passage 30, the radiator 3and the third flow passage 32 is made relatively small (see FIG. 29).Note that the regulating valve 11 also flows the cooling water from thepump 12 to the engine 2.

On the other hand, in the step S124, since the change of a throttleposition is large (NO in step S111), the engine 2 is in a high-loadstate. Therefore, the regulating valve 11 is controlled so that a flowvolume of the cooling water becomes large to promote heat radiation atthe radiator 3, and thereby the temperature of the cooling water isregulated to be the first temperature (80°). Namely, a valve openingposition of the regulating valve 11 is adjusted based on the controlsignal from the controller to close a flow path from the first flowpassage 31 and to fully-open a valve opening position of the downstreamend of the third flow passage 32 (step S124), and thereby the coolingwater is flown only to the second flow passage 30, the radiator 3 andthe third flow passage 32.

Advantages equivalent to those brought by the water-cooling apparatus 1c in the third embodiment, i.e. advantages equivalent to those broughtby the water-cooling apparatus 1 a in the first embodiment or thewater-cooling apparatus 1 b in the second embodiment can be also broughtby the water-cooling apparatus 1 c′ in the present modified example thatis configures as explained above.

The present invention is not limited to the above embodiments. Forexample, an operation state (a low-load state or a high-load state) ofthe engine 2 is judged based on a change of a throttle position in theabove embodiments. However, an operation state of the engine 2 may bejudged based on a vehicle speed, an acceleration of a throttle position,or a combination of these. Specifically, the control will be done basedon judgment of a high-load state when an acceleration of a throttleposition is large, or based on judgment of a low-load state when anacceleration of a throttle position is small.

In addition, the first temperature is 80° C. and the second temperatureis 100° C. in the above embodiments, but the first temperature may be70° C. or the like and, similarly, the second temperature may be 90° C.or the like. The first temperature is lower than the second temperatureand brings most appropriate combustion efficiency in a high-load stateof the engine 2. The second temperature is higher than the firsttemperature and brings most appropriate combustion efficiency in alow-load state of the engine 2.

It should be understood that the present invention includes variousmodifications, and the present invention is limited only by subjectmatters specifying the invention in Claims that are reasonablyunderstood brom the above disclosures.

1. A water-cooling apparatus for an engine that cools an internalcombustion engine by cooling water, the apparatus comprising: a radiatorthat cools the cooling water by heat-exchanging between the coolingwater and air; a first flow passage that flows the cooling water to theengine; a second flow passage that is branched from the first flowpassage and flows the cooling water to the radiator; a third flowpassage that flows the cooling water flowing from the radiator to thefirst flow passage at a downstream from a branched point of the secondflow passage from the first flow passage; a regulating valve that isdisposed on the first flow passage and regulates a flow volume of thecooling water flowing through the radiator; and a pump that is disposedon the first flow passage and circulates the cooling water through theengine and/or the radiator, wherein the regulating valve is configuredto flows the cooling water flowing from the radiator to the first flowpassage when opened.
 2. The water-cooling apparatus for an engineaccording to claim 1, wherein, in a case where temperature of thecooling water that brings most appropriate combustion efficiency in ahigh-load state of the engine is defined as a first temperature, whentemperature of the cooling water in the engine is equal-to orhigher-than the first temperature, the regulating valve closes a flowpath through the second flow passage, the radiator and the third flowpassage.
 3. The water-cooling apparatus for an engine according to claim1, wherein the pump is an electrical pump operable independently fromoperations of the engine.
 4. The water-cooling apparatus for an engineaccording to claim 1, wherein, in a case where temperature of thecooling water that brings most appropriate combustion efficiency in ahigh-load state of the engine is defined as a first temperature, andtemperature of the cooling water that brings most appropriate combustionefficiency in a low-load state of the engine is defined as a secondtemperature higher than the first temperature, when temperature of thecooling water in the engine is equal-to or higher-than the firsttemperature and a change of a throttle position for adjusting an intakeair volume to the engine is small, the regulating valve regulates a flowvolume of the cooling water to a flow path through the second flowpassage the radiator and the third flow passage so that the temperatureof the cooling water is regulated to be the second temperature.
 5. Thewater-cooling apparatus for an engine according to claim 1, wherein in acase where temperature of the cooling water that brings most appropriatecombustion efficiency in a high-load state of the engine is defined as afirst temperature, when temperature of the cooling water in the engineis equal-to or higher-than the first temperature and a change of athrottle position for adjusting an intake air volume to the engine islarge, the regulating valve increases a flow volume of the cooling waterto a flow path through the second flow passage the radiator and thethird flow passage.
 6. The water-cooling apparatus for an engineaccording to claim 1, wherein the engine is inclined with an exhaustside thereof faced downward.